Pixel repair method for a direct view display device

ABSTRACT

A method of repairing a light emitting device assembly includes providing a repair source substrate with an array of first light emitting diodes, providing a first carrier substrate with a temporary adhesive layer thereupon, forming a first assembly including the first carrier substrate and at least one first light emitting diode that is a subset of the array of first light emitting diodes, where the at least one first light emitting diode is attached to the first carrier substrate through a respective portion of the temporary adhesive layer and detached from the repair source substrate, providing a second carrier substrate with a temporary bonding layer thereupon, attaching the at least one first light emitting diode to the temporary bonding layer, detaching the first carrier substrate from each portion of the temporary adhesive layer, removing each portion of the temporary adhesive layer from the at least one first light emitting diode, providing a light emitting device including at least one vacancy location and an array of light emitting diodes bonded to a backplane, and bonding the at least one first light emitting diode to the respective at least one vacancy location within the light emitting device.

FIELD

The embodiments of the invention are directed generally to a pixelrepair method for a direct view display device.

BACKGROUND

Light emitting devices such as light emitting devices are used inelectronic displays, such as liquid crystal displays in laptops or LEDtelevisions. Light emitting devices include light emitting diodes (LEDs)and various other types of electronic devices configured to emit light.A microLED refers to a light emitting diode having lateral dimensionsthat do not exceed 1 mm. A microLED has a typical lateral dimension in arange from 1 microns to 100 microns. An array of microLEDs can form anindividual pixel element. A direct view display device can include anarray of pixel elements, each of which includes at least one microLED,which is typically an array of microLEDs.

A functional direct view display device requires functionality of allpixel elements therein. In case the direct view display device includesan array of microLED's, each of the microLED's needs to be functional inorder for the direct view display device to be fully functional. Achallenge for manufacture of a direct view display device employingmicroLED's is successful transfer of all microLED's required for thedirect view display device. While progress is being made in increasingthe yield of the microLED transfer process to a backplane, a highfraction of microLED transfer processes generate imperfect direct viewdisplay devices in which at least one microLED failed to transfer to thebackplane. In view of the above, a process is desired to for repairingan imperfect direct view display device in which at least one microLEDfailed to transfer to the backplane during a preceding manufacturingprocess.

SUMMARY

According to an aspect of the present disclosure, a method of repairinga light emitting device assembly includes providing a repair sourcesubstrate with an array of first light emitting diodes, providing afirst carrier substrate with a temporary adhesive layer thereupon,forming a first assembly including the first carrier substrate and atleast one first light emitting diode that is a subset of the array offirst light emitting diodes, where the at least one first light emittingdiode is attached to the first carrier substrate through a respectiveportion of the temporary adhesive layer and detached from the repairsource substrate, providing a second carrier substrate with a temporarybonding layer thereupon, attaching the at least one first light emittingdiode to the temporary bonding layer, detaching the first carriersubstrate from each portion of the temporary adhesive layer, removingeach portion of the temporary adhesive layer from the at least one firstlight emitting diode, providing a light emitting device including atleast one vacancy location and an array of light emitting diodes bondedto a backplane, and bonding the at least one first light emitting diodeto the respective at least one vacancy location within the lightemitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a substrate including dies of lightemitting devices according to an embodiment of the present disclosure.

FIGS. 2A-2E are a schematic sequence for transfer of light emittingdevices according to the exemplary transfer pattern illustrated in FIG.1.

FIG. 3A is a vertical cross-sectional view of an exemplary structure forformation of a light emitting device that includes a backplane accordingto an embodiment of the present disclosure.

FIG. 3B is a top-down view of the exemplary structure of FIG. 3A.

FIG. 4 is a vertical cross-sectional view of the exemplary structureafter formation of a continuous insulating material layer over thebackplane according to an embodiment of the present disclosure.

FIG. 5A is a vertical cross-sectional view of the exemplary structureafter formation of insulating material portions by patterning thecontinuous insulating material layer according to first and secondembodiments of the present disclosure.

FIG. 5B is a top-down view of the exemplary structure of FIG. 5Aaccording to the first embodiment of the present disclosure.

FIG. 5C is a top-down view of the exemplary structure of FIG. 5Aaccording to the second embodiment of the present disclosure.

FIG. 6A is a vertical cross-sectional view of the exemplary structureafter formation of a two-dimensional array of metal plate clustersaccording to the first and second embodiments of the present disclosure.

FIG. 6B is a top-down view of the exemplary structure of FIG. 6Aaccording to the first embodiment of the present disclosure.

FIG. 6C is a top-down view of the exemplary structure of FIG. 6Aaccording to the second embodiment of the present disclosure.

FIG. 7A is a vertical cross-sectional view of the exemplary structureafter formation of a two-dimensional array of backplane-side bondingpads according to the first and second embodiments of the presentdisclosure.

FIG. 7B is a top-down view of the exemplary structure of FIG. 7Aaccording to the first embodiment of the present disclosure.

FIG. 7C is a top-down view of the exemplary structure of FIG. 7Aaccording to the second embodiment of the present disclosure.

FIG. 8 is a vertical cross-sectional view of the exemplary structureafter formation of backplane-side solder material portions on thetwo-dimensional array of backplane-side bonding pads according to thefirst and second embodiments of the present disclosure.

FIG. 9 is a vertical cross-sectional view of the exemplary structureafter disposing a first source substrate over the backplane such thatthe first light emitting devices face the backplane according to thefirst and second embodiments of the present disclosure.

FIG. 10 is a vertical cross-sectional view of the exemplary structureafter selective bonding a subset of the first light emitting devices tothe backplane employing a laser irradiation reflow process according tothe first and second embodiments of the present disclosure.

FIG. 11 is a vertical cross-sectional view of the exemplary structureafter selective dissociation of the subset of the first light emittingdevices from the first source substrate employing a selective laserablation process according to the first and second embodiments of thepresent disclosure.

FIG. 12 is a vertical cross-sectional view of the exemplary structureafter separating the assembly of the backplane and the subset of thefirst light emitting devices an assembly of the first source substrateand remaining first light emitting devices according to the first andsecond embodiments of the present disclosure.

FIG. 13 is a vertical cross-sectional view of the exemplary structureafter disposing a second source substrate over the backplane such thatthe second light emitting devices face the backplane according to thefirst and second embodiments of the present disclosure.

FIG. 14A is a vertical cross-sectional view of the exemplary structuretransfer of a set of a first light emitting device, a second lightemitting device, and a third light emitting device to each metal platecluster according to the first and second embodiments of the presentdisclosure.

FIG. 14B is a top-down view of the exemplary structure of FIG. 14Aaccording to the first embodiment of the present disclosure.

FIG. 14C is a top-down view of the exemplary structure of FIG. 14Aaccording to the second embodiment of the present disclosure.

FIG. 15 illustrates a first repair source substrate within an array offirst light emitting diodes and a first carrier substrate with atemporary adhesive layer according to an embodiment of the presentdisclosure.

FIG. 16A illustrates an assembly of the first repair source substrate,the array of first light emitting diodes, a thermally-cured temporaryadhesive layer, and the first carrier substrate according to anembodiment of the present disclosure.

FIG. 16B illustrates an assembly of the first repair source substrate,the array of first light emitting diodes, selectively laser-bondedtemporary adhesive portions embedded in the temporary adhesive layer,and the first carrier substrate according to an embodiment of thepresent disclosure.

FIG. 16C illustrates an assembly of the first repair source substrate,the array of first light emitting diodes, discrete thermally-curedtemporary adhesive portions, and the first carrier substrate accordingto an embodiment of the present disclosure.

FIG. 17A illustrates the assembly of the first carrier substrate, thethermally-cured temporary adhesive layer, and the array of first lightemitting diodes during detachment of first replacement light emittingdiodes from the first repair source substrate according to an embodimentof the present disclosure.

FIG. 17B illustrates the assembly of the first carrier substrate, theselectively laser-bonded temporary adhesive portions embedded in thetemporary adhesive layer, and the array of first light emitting diodesduring detachment of first replacement light emitting diodes from thefirst repair source substrate according to an embodiment of the presentdisclosure.

FIG. 17C illustrates the assembly of the first carrier substrate, thediscrete thermally-cured temporary adhesive portions, and the array offirst light emitting diodes during detachment of first replacement lightemitting diodes from the first repair source substrate according to anembodiment of the present disclosure.

FIG. 18A illustrates the assembly of the first carrier substrate, thethermally-cured temporary adhesive layer, and the first replacementlight emitting diodes after detachment from the first repair sourcesubstrate according to an embodiment of the present disclosure.

FIG. 18B illustrates the assembly of the first carrier substrate, theselectively laser-bonded temporary adhesive portions embedded in thetemporary adhesive layer, and the first replacement light emittingdiodes after detachment from the first repair source substrate accordingto an embodiment of the present disclosure.

FIG. 18C illustrates the assembly of the first carrier substrate, thediscrete thermally-cured temporary adhesive portions, and the firstreplacement light emitting diodes after detachment from the first repairsource substrate according to an embodiment of the present disclosure.

FIG. 19 illustrates the assembly of the first carrier substrate, thethermally-cured temporary adhesive layer, and the first replacementlight emitting diodes after placement over a layer stack including asecond carrier substrate, a backside release layer, and a temporarybonding layer according to an embodiment of the present disclosure.

FIG. 20 illustrates the assembly of the first carrier substrate, thethermally-cured temporary adhesive layer, the first replacement lightemitting diodes, and the layer stack of the second carrier substrate,the backside release layer, and the temporary bonding layer according toan embodiment of the present disclosure.

FIG. 21A illustrates the assembly of the thermally-cured temporaryadhesive layer, the first replacement light emitting diodes, and thelayer stack of the second carrier substrate, the backside release layer,and the temporary bonding layer after detaching the first carriersubstrate according to an embodiment of the present disclosure.

FIG. 21B illustrates the assembly of the selectively laser-bondedtemporary adhesive portions embedded in the temporary adhesive layer,the first replacement light emitting diodes, and the layer stack of thesecond carrier substrate, the backside release layer, and the temporarybonding layer after detaching the first carrier substrate according toan embodiment of the present disclosure.

FIG. 21C illustrates the assembly of the thermally-cured temporaryadhesive portions, the first replacement light emitting diodes, and thelayer stack of the second carrier substrate, the backside release layer,and the temporary bonding layer after detaching the first carriersubstrate according to an embodiment of the present disclosure.

FIG. 22 illustrates the assembly of the first replacement light emittingdiodes, and the layer stack of the second carrier substrate, thebackside release layer, and the temporary bonding layer after optionaldicing of the assembly into multiple coupons according to an embodimentof the present disclosure.

FIG. 23 illustrates a direct view device with missing light emittingdiodes and the assembly of the first replacement light emitting diodes,and the layer stack of the second carrier substrate, the backsiderelease layer, and the temporary bonding layer after alignment accordingto an embodiment of the present disclosure.

FIG. 24 illustrates the direct view device after bonding the firstreplacement light emitting diodes according to an embodiment of thepresent disclosure.

FIG. 25 illustrates the direct view device after detaching the secondcarrier substrate and the backside release layer according to anembodiment of the present disclosure.

FIG. 26 illustrates the direct view device after removing the temporarybonding layer according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure is directed to a pixel repairmethod for a direct view display device, the various aspects of whichare described below. Throughout the drawings, like elements aredescribed by the same reference numeral. The drawings are not drawn toscale. Multiple instances of an element may be duplicated where a singleinstance of the element is illustrated, unless absence of duplication ofelements is expressly described or clearly indicated otherwise. Ordinalssuch as “first,” “second,” and “third” are employed merely to identifysimilar elements, and different ordinals may be employed across thespecification and the claims of the instant disclosure.

As used herein, a “light emitting device” refers to any device that isconfigured to emit light and includes, but is not limited to, a lightemitting device (LED), a laser, such as a vertical-cavitysurface-emitting laser (VCSEL), and any other electronic device that isconfigured to emit light upon application of a suitable electrical bias.A light emitting device may be a vertical structure (e.g., a verticalLED) in which the p-side and n-side contacts are located on oppositesides of the structure or a lateral structure in which the p-side andn-side contacts are located on the same side of the structure. As usedherein, a “light emitting device assembly” refers to an assembly inwhich at least one light emitting device is structurally fixed withrespect to a carrier structure, which can include, for example, asubstrate, a matrix, or any other structure configured to provide stablemechanical support to the at least one light emitting device.

In the present disclosure, a method is provided for transferring anarray of devices (such as an array of light emitting devices or an arrayof sensor devices) from a growth substrate to a target substrate. Thetarget substrate can be any substrate on which formation of multipletypes of devices in any configuration is desired. In an illustrativeexample, the target substrate can be a backplane substrate such as anactive or passive matrix backplane substrate for driving light emittingdevices. As used herein, a “backplane” or a “backplane substrate” refersto any substrate configured to affix multiple devices thereupon. In oneembodiment, the center-to-center spacing of neighboring light emittingdevices on the backplane substrate can be is an integer multiple of thecenter-to-center spacing of neighboring light emitting devices on thegrowth substrate. The light emitting devices may include a plurality oflight emitting devices, such as a group of two light emitting devices,one configured to emit blue light and one configured to emit greenlight. The light emitting devices may include a group of three lightemitting devices, one configured to emit blue light, one configured toemit green light, and one configured to emit red light. As used herein,“neighboring light emitting devices” refer to a plurality of two or morelight emitting devices located in closer proximity than at least anotherlight emitting device. The method of the present disclosure can provideselective transfer of a subset of light emitting devices from a lightemitting device array on a growth substrate to the backplane substrate.

Devices of a same type can be fabricated on respective initial growthsubstrates. As used herein, an “initial growth substrate” refers to asubstrate that is processed to form devices thereupon or therein. Thedevices can include light emitting devices and/or sensor devices (e.g.,photodetectors) and/or any other electronic devices. The light emittingdevices can be any type of light emitting devices, i.e., vertical lightemitting diodes, lateral light emitting diodes, or any combinationthereof. Devices of the same type can be formed on each initial growthsubstrate, the types being different from one initial growth substrateto another. The devices can be formed as an array on the respectiveinitial growth substrates.

Utilization of a high percentage of light emitting devices asmanufactured on an initial growth substrate for incorporation intobackplanes is an essential component of economically manufacturing adirect view light emitting device assembly. Generally, a light emittingdevice assembly provides a rectangular viewing area, while initialgrowth substrates typically have circular device areas. After transferof light emitting devices from a rectangular region of an initial growthsubstrate to a backplane, a circular substrate can have unutilizedregion from which devices are not transferred. Methods of the presentdisclosure provide methods for utilizing the complement of a rectangularcenter area of an initial growth substrate, or in case devices aretransferred to a transfer substrate, for utilizing the complement of arectangular center area of a transfer substrate.

The methods of the present disclosure employ one of more of thefollowing methods. In some embodiments, dies (i.e., instances of a lightemitting device) can be transferred to a temporary support system andplaced on a backplane one by one. In some embodiments, defect maps canbe supplied to a temporary repair template substrate, and can beattached to a backplane in parallel. In some embodiment, local areareplacement or patterned pixel transfer can be employed.

Referring to FIG. 1, a substrate including dies of light emitting diodes10 is illustrated. The substrate may include an edge exclusion region300 at a periphery, in which devices are not formed. The substrate caninclude light emitting devices of a same type (which is herein referredto as first type) arranged in a first array configuration. The lightemitting devices of the first type are multiple instances of the samedevice, which may be, for example, light emitting devices that emitlight at a same peak wavelength. For example, the light emitting devicesof the first type may be red light emitting devices, green lightemitting devices, or blue light emitting devices.

The first array configuration has a primary-direction pitch Px1 along arespective primary direction (i.e., the primary direction of the firstarray configuration) and has a secondary-direction pitch Py1 along arespective secondary direction (i.e., the secondary direction of thefirst array configuration). As used herein, a primary direction and asecond direction of an array configuration refer to two directions alongwhich a unit cell of the array configuration is repeated. In arectangular array configuration, the primary direction and the seconddirection may be perpendicular to each other, and are referred to as anx-direction and a y-direction.

The light emitting diodes 10 on the substrate can be transferred tomultiple backplanes having bonding sites in the second arrayconfiguration. A predetermined transfer pattern and a predeterminedtransfer sequence can be employed for transfer of the light emittingdiodes 10. Light emitting devices of different types provided fromadditional substrates can be employed in conjunction with the lightemitting diodes 10 from the substrate to provide a functional directview light emitting device assembly.

Referring to FIGS. 2A-2E, an exemplary transfer pattern and an exemplarytransfer sequence are illustrated for transferring three different typesof devices (10B, 10G, 10R) (e.g., blue, green and red emitting LEDs,respectively) to four backplanes (BP1, BP2, BP3, BP4). The threedifferent types of devices (10B, 10G, 10R) can be provided on threesource substrates (B, G, R), which can comprise three transfersubstrates, or three growth substrates, or combinations thereof. Thefirst light emitting diodes 10B can be provided on the first sourcesubstrate B, the second light emitting diodes 10G can be provided on thesecond source substrate G, and the third light emitting diodes 10R canbe provided on the third source substrate R.

Changes in the presence or absence of the various devices (10B, 10G,10R) on the source substrates (B, G, R) and the backplanes (BP1, BP2,BP3, BP4) at each step of the transfer sequence are illustrated in FIGS.2A-2E. FIG. 2A corresponds to a configuration prior to any transfer ofthe devices (10B, 10G, 10R), FIG. 2B corresponds to the configurationafter performing transfer steps 1-3, FIG. 2C corresponds to theconfiguration after performing steps 4-6, FIG. 2D corresponds to theconfiguration after performing steps 7-9, and FIG. 2E corresponds to theconfiguration after performing steps 10-12. It should be noted thatsteps 1-3 as illustrated in FIG. 2B may be shuffled in any order becausesteps 1-3 are independent of one another, steps 4-6 as illustrated inFIG. 2C may be shuffled in any order because steps 4-6 are independentof one another, steps 7-9 as illustrated in FIG. 2D may be shuffled inany order because steps 7-9 are independent of one another, and steps10-12 as illustrated in FIG. 2E may be shuffled in any order becausesteps 10-12 are independent of one another.

While the exemplary transfer pattern and the exemplary transfer sequenceis illustrated for cases in which four source substrates (B, G, R) andfour backplanes (BP1, BP2, BP3, BP4) are employed, the method of thepresent disclosure can be applied to any case in which m transferassemblies and n backplanes are employed, in which m is an integergreater than 1, n is an integer greater than 1, and n is not less thanm. The n backplanes bond with devices from the m transfer assemblies toform n integrated light emitting device assemblies. In one embodiment, ncan be the same as, or greater than, m.

A plurality of transfer assemblies, e.g., m transfer assemblies, isprovided. Each of the m transfer assemblies comprises a respectivesource substrate (B, G, R) and respective devices (10B, 10G, 10R) withina two-dimensional array having a same two-dimensional periodicity. Asused herein, a same two-dimensional periodicity for multiple structuresrefers to a configuration in which each of the multiple structures has arespective unit structure and instances of the respective unit structureare repeated along two independent directions of periodicity (e.g., afirst periodicity direction and a second periodicity direction), and theunit structures are repeated along the respective first periodicitydirection with a same first pitch and are repeated along the respectivesecond periodicity direction with a same second pitch for all of themultiple structures, and the angle between the first periodicitydirection and the second periodicity direction is the same for all ofthe multiple structures. Each of the n backplanes has a periodicrepetition of respective unit conductive bonding structures patternconfigured to mount m types of devices.

Each of the m types of devices can be one of the devices within arespective transfer assembly among the m transfer assemblies. Thepitches of each unit conductive bonding structures pattern along twoindependent directions within each of the n backplanes can be multiplesof a respective pitch of the two-dimensional periodicity of the deviceswithin each of the m transfer assemblies. In an illustrative example,each of the devices (10B, 10G, 10R) can be periodic within a respectivetransfer assembly with the first periodicity of a along a firstdirection, and with the second periodicity of b along a second direction(which may be perpendicular to the first direction). The unit conductivebond pad pattern within each of the backplanes can have the firstperiodicity of 2 a (which is an integer multiple of a) along a firstdirection, and with the second periodicity of 2 b (which is an integermultiple of b) along a second direction (which may be perpendicular tothe first direction).

Subsets of devices (10B, 10G, 10R) from each of the m transferassemblies can be sequentially transferred to a respective backplane(BP1, BP2, BP3, BP4) among the n backplanes by disposing each respectivetransfer assembly over the respective backplane (BP1, BP2, BP3, BP4) atlocations that preclude collision of existing devices on the respectivetransfer assembly with any devices (10B, 10G, 10R), if any, that arepreviously bonded to the respective backplane (BP1, BP2, BP3, BP4).

In one embodiment, a unit cell U1 of the second array configuration ofthe light emitting device assembly can be defined by a rectangle havinga first pair of sides having a first length of the secondprimary-direction pitch Px2 along a respective primary direction andhaving a second pair of sides having a second length of the secondsecondary-direction pitch Py2 along a respective secondary direction. Inone embodiment, the unit cell U1 can include a first-type light emittingdiode 10R (which may be a red light emitting device), a second-typelight emitting diode 10G (which may be a green light emitting device), athird-type light emitting diode 10B (which may be a blue light emittingdevice), and a respective empty site 10E configured to accommodate arespective repair light emitting device.

If each of the first, second, and third-type light emitting devices(10R, 10G, 10B) of a pixel is functional, such a pixel is a functionalpixel, and attachment of any repair light emitting device to the pixelis not necessary. If any of the first, second, and third-type lightemitting devices (10R, 10G, 10B) of a pixel is defective, i.e.,non-functional, such a pixel is a defective, i.e., non-functional,pixel, and attachment of a repair light emitting device to the pixel isnot necessary. In this case, the empty site 10E of such a defectivepixel is employed to attach a repair light emitting device. Each employsite 10E of the defective pixels is a repair site to which a repairlight emitting device needs to be attached.

In general, the light emitting device assembly includes a backplane andinstances of light emitting devices of the first type at bonding sitesin the second array configuration. Repair sites can be identified forany given light emitting device assembly, which may be formed employingthe light emitting devices from the substrate including the base pitchregion 100, and/or employing light emitting devices from additionalsubstrates. In one embodiment, a first set of repair sites can bedefined based on the functionality of one type of light emittingdevices, e.g., light emitting devices of the first type. Each of thefirst set of repair sites can be an empty site 10E configured toaccommodate a respective repair light emitting device. Each of the firstset of repair sites can be located within a pixel including a defectiveinstance of the light emitting device of the first type.

Referring to FIGS. 3A and 3B, a backplane 40 is provided, which can beemployed as any of the four backplanes (BP1, BP2, BP3, BP4) describedabove. The backplane 40 includes the substrate 42 containing metalinterconnect structures (46, 44, 425) located on the substrate 42 and/orembedded within the substrate 42. The substrate 42 can be opticallytransparent or optically opaque. As used herein, an “opticallytransparent” element or a “transparent” element refers to an elementthat transmits at least 50% of light over more than 90% of the visiblespectrum range, i.e., the wavelength range from 400 nm to 800 nm. If thesubstrate 42 is optically transparent then it may transmit more than 50%of light at the wavelength of an optional laser beam to be subsequentlyemployed to induce reflow of solder materials in a bonding process, if alaser reflow process is used.

In one embodiment, the substrate 42 can include a first dielectricmaterial having a first elastic modulus, i.e., a first Young's modulus.In one embodiment, the substrate 42 can include any dielectric materialthat can be employed to provide a printed circuit board (PCB) as knownin the art. In one embodiment, the metal interconnect structures (46,44, 425) can be laid out on and/or within the substrate 42 to providegap regions GR in which the metal interconnect structures (46, 44, 425)are not present. In one embodiment, the gap regions GR can be arrangedas a periodic two-dimensional array. The pitch of the gap regions GRalong a first horizontal direction hd1 can be an integer M times theprimary-direction pitch Px1 of the light emitting diodes 10 describedabove, and the pitch of gap regions GR along a second horizontaldirection hd2 can be an integer M times the secondary-direction pitchPy1 of the light emitting diodes 10 described above.

The metal interconnect structures (46, 44, 425) are arranged to provideelectrically conductive paths to the light emitting devices to besubsequently attached to the front side of the backplane 40. In anillustrative example, the metal interconnect structures (46, 44, 425)can include an array of conductive via structures 46 having physicallyexposed surfaces on the front side of the backplane 40. Further, themetal interconnect structures (46, 44, 425) can include metal lines 44that extend horizontally to provide lateral electrical connectionbetween a respective conductive via structures 46 and additional metalinterconnect structures 425, which may include additional metal viastructures, additional metal line structures, and/or conductive traces.In one embodiment, physically exposed components of the metalinterconnect structures (46, 44, 425), such as the conductive viastructures 46, can be arranged as a two-dimensional periodic arrayhaving the same two-dimensional periodicity as the two-dimensional arrayof gap regions GR.

The backplane 40 can have a non-planar top surface that can be caused byintentionally formed local dimples and/or protrusions and/or caused byunintentional distortion such as bowing, bending, and/or arching of thesubstrate 42. Such a non-planar top surface causes physically exposedsurfaces of the conductive via structures 46 to be located at differentlevels and/or to have tilted top surfaces. Bonding light emittingdevices on vertically offset surfaces and/or tilted physically exposedsurfaces of the conductive via structures 46 can result in degradationof quality of bonding, and may induce electrical opens and/or otherstructural defects. According to an embodiment of the presentdisclosure, additional structures are formed over the backplane 40 priorto bonding the light emitting devices to provide horizontal bondingsurfaces located within a same two-dimensional, substantially horizontalplane. As used herein, a “two-dimensional” plane refers to a Euclideanplane and excludes Riemannian (curved) planes.

Referring to FIG. 4, a second dielectric material having a secondelastic modulus is formed over the backplane 40 as a continuousinsulating material layer 48L. The second dielectric material can be anoptically transparent or opaque material, and can have an elasticmodulus that is less than the first elastic modulus. For example, thesecond elastic modulus can be less than 80% of the first elasticmodulus, and may be in a range from 1% to 60% of the first elasticmodulus to provide an increased level of elasticity to bonding padsduring a subsequent bonding process. For example, the second insulatingmaterial layer 48L can include, and/or can consist essentially of, anepoxy based polymer, such as SU-8 negative photoresist material, asilicone-based polymer material, a benzocyclobutene-based (BCB) polymer,or other organic polymer materials. In one embodiment, the secondinsulating material layer 48L can include a self-planarizing polymermaterial that can be applied and cured to provide a planar top surfacethat extends over the entirety of the non-planar top surface of thebackplane 40. The thickness of the continuous insulating material layer48L can be in a range from 200 nm to 20 microns, although lesser andgreater thicknesses can also be employed.

Referring to FIGS. 5A-5C, the continuous insulating material layer 48Lcan be patterned to form at least one opening therethrough. FIG. 5A is avertical cross-sectional view that is the same for a first embodimentand a second embodiment, FIG. 5B is a top-down view for the firstembodiment, and FIG. 5C is a top-down view for a second embodiment. Forexample, a photoresist layer (not shown) can be applied over thecontinuous insulating material layer 48L, and can be lithographicallypatterned to form at least one opening therein. The pattern of theopenings is selected such that each area of the gap region GR iscompletely covered by the patterned photoresist layer. An etch processcan be performed to remove portions of the continuous insulatingmaterial layer 48L that are not covered by the patterned photoresistlayer. The etch process can be an isotropic etch process (such as a wetetch process), or can be an anisotropic etch process (such as a reactiveion etch process). The continuous insulating material layer 48L ispatterned by the etch process to provide insulating material portions48. Each insulating material portion 48 overlies a respective gap regionGR, and may laterally extend further to cover peripheral areas thatlaterally surround the respective gap region GR. The photoresist layercan be subsequently removed, for example, by ashing.

In the first embodiment illustrated in FIGS. 5A and 5B, the at least oneopening through the photoresist layer, and consequently, the at leastone opening 49 that is formed through the continuous insulating materiallayer 48L may include a first set of line trenches laterally extendingalong the first horizontal direction hd1 and a second set of linetrenches laterally extending along the second horizontal direction hd2.The second horizontal direction hd2 can be perpendicular to the firsthorizontal direction hd1, and the areas of the first set of linetrenches and the second set of line trenches can be selected not toinclude any of the areas of the gap regions GR. In this case, theinsulating material portions 48 may be formed as a two-dimensional arrayof insulating mesa structures each having a horizontal top surface suchthat all the horizontal top surfaces of the insulating material portions48 are within a same horizontal plane. Top surfaces of the underlyingmetal interconnect structures (46, 44, 425) can be physically exposedbetween neighboring pairs of the insulating material portions 48. Theinsulating material portions 48 are arranged as a two-dimensional arrayof insulating mesa structures not directly contacting one another andhaving a same two-dimensional periodicity as the two-dimensional arrayof gap regions GR. The insulating material portions 48 may have taperedsidewalls or vertical sidewalls.

In the second embodiment illustrated in FIGS. 5A and 5C, the at leastone opening through the photoresist layer, and consequently, the atleast one opening 49 that is formed through the continuous insulatingmaterial layer 48L may include discrete openings 49 that overlie arespective one of the conductive via structures 46. A center portion ofthe top surface of each conductive via structure 46 can be physicallyexposed underneath each discrete opening through the continuousinsulating material layer 48L. In this case, the insulating materialportions 48 may be formed portions of the continuous insulating materiallayer 48L that overlie the gap regions GR. In other words, the areas ofthe gap regions GR can define the areas of the insulating materialportions 48, which can be continuously connected to other insulatingmaterial portions 48 within the continuous insulating material layer48L. The planar horizontal surface regions of the insulating materialportions 48 are within the same horizontal plane. Top surfaces of theunderlying metal interconnect structures (46, 44, 425) can be physicallyexposed between neighboring pairs of the insulating material portions48. Each opening in the continuous insulating metal layer 48L may havetapered sidewalls or vertical sidewalls.

Referring to FIGS. 6A-6C, a two-dimensional array of metal plateclusters can be formed over the two-dimensional array of insulatingmaterial portions 48. In one embodiment, a continuous metal layer can bedeposited over the insulating material portions 48 and on top surfacesof the metal interconnect structures (46, 44, 425) that are physicallyexposed in the openings 49, such as the physically exposed top surfacesof the conductive via structures 46. The continuous metal layer can besubsequently patterned to form a two-dimensional array of metal plateclusters. Alternatively, the two-dimensional array of metal plateclusters can be formed by forming a patterned photoresist layer,depositing a metal layer employing a non-conformal deposition process(such as physical vapor deposition or vacuum evaporation), and bylifting off the patterned photoresist layer.

Each patterned portion of the continuous metal layer constitutes a metalplate 34. A cluster of metal plates 34 overlies each insulating materialportion 48, which overlies a respective gap region GR. Each set ofpatterned portions of the continuous metal layer overlying a sameinsulating material portion 48 constitutes a metal plate cluster. Thetwo-dimensional array of metal plate clusters includes a first metallicmaterial, which may be a barrier metallic material having a relativelyhigh melting point to prevent damage during a subsequent bonding processthat reflows a solder material. For example, the first metallic materialcan include, or consist essentially of, tungsten, titanium, tantalum,tungsten nitride, tantalum nitride, titanium nitride, or a combinationthereof. The thickness of each metal plate 34 can be selected to providesufficiently low electrical resistance without excessively increasingthermal mass (which can reduce effectiveness during a subsequent bondingprocess). For example, the thickness of each metal plate 34 can be in arange from 300 nm to 12 microns, although lesser and greater thicknessescan also be employed.

Generally, a two-dimensional array of metal plate clusters is formedover the two-dimensional array of insulating material portions 48 withthe same two-dimensional periodicity. Each of the metal plate clusterscomprises a plurality of metal plates 34. Each metal plate 34 includes ahorizontal metal plate portion 34H overlying a planar top surface regionof a respective insulating material portion 48 and a connection metalportion 34C extending between the horizontal metal plate portion 34H anda respective one of the metal interconnect structures (46, 44, 425).Each of the connection metal portions 34C can be formed directly on atapered sidewall or a vertical sidewall of a respective one of theinsulating material portions 48 and a top surface of a respective metalinterconnect structure (46, 44, 425), such as a top surface of aconductive via structure 46.

In the first configuration illustrated in FIGS. 6A and 6B, theinsulating material portions 48 are arranged as a two-dimensional arrayof insulating mesa structures not directly contacting one another andhaving the same two-dimensional periodicity as the two-dimensional arrayof metal plate clusters. In the second configuration illustrated inFIGS. 6A and 6C, each connection metal portion 34C extends through arespective opening 49 through the continuous insulating material layerthat includes the two-dimensional array of insulating material portions48, which overlies, and has the same two-dimensional periodicity as, thetwo-dimensional array of gap regions GR.

Referring to FIGS. 7A-7C, a two-dimensional array of backplane-sidebonding pads 36 can be formed by deposition and patterning of at leastone second metallic material. In one embodiment, the second materiallayer can be deposited as a continuous metallic material layer, and aphotoresist layer can be applied and patterned over the continuousmetallic material layer. An etch process can be performed to remove thesecond metallic material selective to the first metallic material,thereby patterning the continuous metallic material layer into thetwo-dimensional array of backplane-side bonding pads 36. Alternatively,a patterned photoresist layer can be employed as a mask layer, and thesecond metallic material can be anisotropically deposited on physicallyexposed surfaces of the metal plates 34 and over the patternedphotoresist layer. A lift-off process can be employed to remove thepatterned photoresist layer and portions of the second metallic materiallayer thereupon. Remaining portions of the second metallic materialconstitute the two-dimensional array of backplane-side bonding pads 36.The two-dimensional array of backplane-side bonding pads 36 is formed ontop of the two-dimensional array of metal plate clusters. The secondmetallic material of the backplane-side bonding pads 36 can have ahigher thermal conductivity than the first metallic material, and canhave a lower melting point than the first metallic material. Forexample, the second metallic material can include copper or acopper-containing metal alloy.

In one embodiment, each of the backplane-side bonding pads 36 can beformed on a respective one of the horizontal metal plate portions 34H. Aset of M×N backplane-side bonding pads 36 can be formed as an M×Nrectangular periodic array over a respective insulating material portion48. In one embodiment, the pitch of the two-dimensional array of metalplate clusters along the first horizontal direction hd1 can be M timesthe primary-direction pitch Px1, and the pitch of the two-dimensionalarray of metal plate clusters along the second horizontal direction hd2can be N times the secondary-direction pitch Py1. In this case, theentire set of backplane-side bonding pads 36 can be formed as atwo-dimensional periodic array having the periodicity of theprimary-direction pitch Px1 along the first horizontal direction hd1 andhaving the periodicity of the secondary-direction pitch Py1 along thesecond horizontal direction hd2.

Referring to FIG. 8, optional backplane-side solder material portions 38can be formed on the two-dimensional array of backplane-side bondingpads 36. Alternatively, the backplane-side bonding pads 36 can be formedof a solder material and the backplane-side solder material portions 38can be omitted.

Referring to FIG. 9, a first source substrate 8A with first lightemitting diodes 10B is provided. The first source substrate 8A includesan optically transparent material such as sapphire. A layer stackincluding an undoped III-V compound material layer, an n-doped III-Vcompound material layer, a multi-quantum-well layer, a p-doped compoundsemiconductor layer, and a transparent conductive layer can besequentially formed on the first source substrate 8A during manufactureof first light emitting diodes 10B.

Insulating material portions 16 including a dielectric material (such assilicon oxide, silicon nitride, aluminum oxide, etc.) can be formed todelineate the lateral extent of each first light emitting diode 10B.Dicing channels 19 can be formed through the layer stack to divide thelayer stack into stacks of an undoped III-V compound material layer 11and a first light emitting diode 10B. Each first light emitting diode10B can include a vertical stack of an n-doped III-V compound materiallayer 12, an active region, such as a multi-quantum-well 13, a p-dopedIII-V compound semiconductor layer 14, and a transparent conductivelayer. 15. In a non-limiting illustrative example, each undoped III-Vcompound material layer 11 can include undoped gallium nitride, eachn-doped III-V compound material layer 12 can include n-doped galliumnitride or indium gallium nitride, each multi-quantum-well 13 caninclude a periodic repetition of gallium nitride layers and indiumgallium nitride layers, each p-doped III-V compound semiconductor layer14 can include p-doped gallium nitride or aluminum gallium nitride,and/or each transparent conductive layer 15 can include a transparentconductive oxide, such as indium tin oxide. Layer 12 can be a bulk layeror a plurality of nanowires. The active region 13 and the layer 14 canbe planar layers or nanowire shells. The first light emitting diodes 10Bemit light at a first peak wavelength (e.g., in the blue wavelengthrange).

A device-side bonding pad 17 can be formed on each first light emittingdiode 10B. Each device-side bonding pad 17 can include bonding padmaterial such as Ni, Au, and/or Cu. Optionally, a device-side soldermaterial portion 18 can be formed on each device-side bonding pad 17.The device-side solder material portions 18 can include, for example, alead-free solder material.

The first source substrate 8A can be disposed over the backplane 40 withfirst solder material portions (18, 38) therebetween such that thedevice-side bonding pads 17 of the first light emitting diodes 10B facethe backplane-side bonding pads 36 through the first solder materialportions (18, 38). The first source substrate 8A and the first lightemitting diodes 10B can be aligned such that pairs of a source-sidesolder material portion 18 and a device-side solder material portion 38make direct contact, or are placed in sufficient proximity to inducemerging therebetween upon reflow.

Referring to FIG. 10, a subset of the first light emitting diodes 10B isselectively bonded to the backplane 40. Any suitable selective bondingprocess may be used. For example, selective laser bonding or thermal(e.g., furnace) bonding process may be used to reflow the soldermaterial portions (18, 38).

For example, as shown in FIG. 10, in one embodiment, the bonding processcomprises laser bonding employing a laser irradiation reflow process. Aheating laser can be employed to bond a selected subset of the firstlight emitting diodes 10B to the backplane 40. The pattern of selectionfor the selected subset of the first light emitting diodes 10B can be,for example, the pattern illustrated in FIG. 2B. Specifically, bondingof the selected subset of the first light emitting diodes 10B to thebackplane 40 can be performed by irradiating a first laser beam (77A or77B) to at least one solder material portion (18, 38) to reflow the atleast one solder material portion (18, 38).

In one embodiment, the first laser beam 77A can pass through the firstsubstrate 8A and through the selected subset of first light emittingdiodes 10B to the at least one solder material portion (18, 38) toreflow the at least one solder material portion (18, 38).

In another embodiment, if the backplane substrate 42 is opticallytransparent, then the first laser beam 77B can pass through thebackplane to heat the at least one solder material portion (18, 38). Thefirst laser beam 77B of the heating laser can pass through the gapregion GR of the substrate 42 to avoid collateral heating of metalinterconnect structures (46, 44, 425) other than the irradiated metalplate 34, the irradiated backplane-side bonding pad 36, and theirradiated solder material portions (18, 38). In one embodiment, theheating laser may employ infrared wavelength. For example, the heatinglaser can be a visible or infra-red laser having a wavelength in a rangefrom 0.4 micron to 20 microns, such as 1 to 2 microns, to avoid heatingof the backplane 40, while heating the at least one solder materialportion (18, 38). In another embodiment, both laser beams (77A, 77B) canbe used to irradiate the at least one solder material portion (18, 38)either simultaneously or sequentially.

In another alternative embodiment, a thermal (e.g., furnace) bondingprocess rather than a laser process may be used to reflow the soldermaterial portions (18, 38). In this embodiment, the solder materialportions 18 have a different composition and a different melting point,as described in U.S. Pat. No. 9,893,041 B2, incorporated herein byreference in its entirety. In the thermal bonding process, the lowestmelting point solder material portions (18, 38) are reflowed and bondedfirst at a temperature above their respective melting point but belowthe respective melting point of the other solder material portions whichare not bonded. Subsequently, the next lowest melting point soldermaterial portions (18, 38) are reflowed and bonded second at atemperature above their respective melting point but below therespective melting point of the remaining higher melting point soldermaterial portions which are not bonded. This process is repeated as manytimes as needed to sequentially bond all the pairs of solder materialportions.

The heated and reflowed at least one solder material portion (18, 38)solidifies into a bonded solder material portion 58, which providesbonding between the backplane 40 and a respective first light emittingdiodes 10B through a backplane-side bonding pad 36, a metal plate 34,and a device-side bonding pad 17. A subset, but not all, of the firstlight emitting diodes 10B can be bonded to the backplane 40 byselectively reflowing a subset of the first solder material portions(18, 38).

Referring to FIG. 11, the subset of the first light emitting diodes 10Bthat are bonded to the backplane 40 can be selectively dissociated fromthe first source substrate 8A employing a selective laser ablationprocess. Each bonded light emitting diode 10 can be dissociated from thefirst source substrate 8A by irradiating a second laser beam 87 throughthe first source substrate 8A and onto each III-V compound materiallayer 11 in contact with the bonded first light emitting diodes 10B. Inone embodiment, the first source substrate 8A comprises sapphire, andeach III-V compound material layer 11 comprises a compound semiconductormaterial (such as an undoped III-V compound semiconductor material). Inthis case, the second laser beam 87 ablates each III-V compound materiallayer 11 in contact with the bonded first light emitting diodes 10B. Thewavelength of the laser (which is herein referred to an “ablationlaser”) employed to provide the second laser beam 87 can be different(e.g., shorter) from the wavelength of the heating laser. The wavelengthof the ablation laser can be, for example between 0.1 and 0.75 micron,such as 0.25 to 0.5 micron. In one embodiment, the wavelength of theablation laser can be within an ultraviolet range, i.e., within a rangefrom 10 nm to 400 nm. Each first light emitting diode 10B that is bondedto the backplane 40 through a respective reflowed and re-solidifiedsolder material portion 58 can be dissociated employing laser ablationof the compound semiconductor material (i.e., the material of the III-Vcompound material layer 11) located between the first source substrate8A and each first light emitting diode 10B that is bonded to thebackplane 40.

Referring to FIG. 12, an assembly of the backplane 40 and the set of allfirst light emitting diodes 10B bonded thereto can be separated from anassembly of the first source substrate 8A and the set of all first lightemitting diodes 10B that are not bonded to the backplane 40. Residualportions of the III-V compound material layer 11 can be present on thedistal surfaces of the first light emitting diodes 10B that are attachedto the backplane 40. Specifically, compound semiconductor materialportions 11′ having irregular surface height variations can be locatedon the distal surfaces of the first light emitting diodes 10B. Thedistal surfaces are surfaces of the first light emitting diodes 10Bfacing away from the backplane 40.

Referring to FIG. 13, second light emitting diodes 10G can betransferred as illustrated in FIG. 2C. A second source substrate 8B withsecond light emitting diodes 10G thereupon can be provided. The secondlight emitting diodes 10G emit light at a second peak wavelength (e.g.,in the green visible range) that is different from the first wavelength(e.g., in the blue visible range). The second source substrate 8B canhave the same structural and compositional characteristics as the firstsource substrate 8A. The second light emitting diodes 10G can be formedin the same manner as the first light emitting diodes 10B withmodifications in material compositions to shift the second wavelengthfrom the first wavelength. The second source substrate 8B can bedisposed over the backplane 40 with second solder material portions (38,18) therebetween such that the device-side bonding pads 17 of the secondlight emitting diodes 10G face a subset of the backplane-side bondingpads 36 through the second solder material portions (18, 38). A subset,but not all, of the second light emitting diodes 10G can be bonded tothe backplane 40 by selectively reflowing a subset of the second soldermaterial portions (18, 38). The pattern of selection for the bonded setof second light emitting diodes 10G can be the pattern illustrated inFIG. 2C. The processing steps of FIG. 10 can be employed mutandismutatis for the bonding process that selectively bonds a subset of thesecond light emitting diodes 10G to the backplane 40.

Subsequently, the processing steps of FIG. 11 can be performed mutandismutatis to dissociate all second light emitting diodes 10G that arebonded to the backplane 40 from the second transparent substrate 8B.

Referring to FIGS. 14A-14C, the processing steps of FIGS. 9-11 can berepeatedly performed with necessary changes to bond multiple types oflight emitting diodes (10B, 10G, 10R) to the two-dimensional array ofmetal plate clusters. For example, red light emitting diodes 10R can bebonded to the backplane 40. Each set of light emitting diodes (10B, 10G,10R) attached to a metal plate cluster constitutes a light emittingdevice cluster 50 which can constitute a pixel of a direct view displaydevice, and each of the light emitting diodes can be a subpixel of thedirect view display device. The light emitting luster 50 is configuredto provide an arbitrary color that can be generated by combination oflight of multiple peak wavelengths with different intensities. The lightemitting luster 50 can have any suitable shape and configuration and canhave any suitable number of light emitting devices (i.e., any suitablenumber of LEDs) (10B, 10G, 10R). For example, each light emitting luster50 can include two red light emitting LEDs 10R, one blue light emittingLED 10B and one greed light emitting LED 10G. The red light emittingLEDs 10R can be located next to each other or diagonally from each otherin each light emitting luster 50. Thus, a two-dimensional array of lightemitting device clusters 50 can be bonded to the backplane 40 throughrespective bonding structures (36, 48, 17). Each light emitting devicecluster 50 comprises a plurality of light emitting devices (10B, 10G,10R) overlying a respective metal plate cluster.

Referring to all drawings and according to various embodiments of thepresent disclosure, a light emitting device assembly is provided, whichcomprises: a backplane 40 comprising the substrate 42 and embeddingmetal interconnect structures (46, 44, 425) therein; insulating materialportions 48 including a respective planar top surface region and locatedover the backplane 40, wherein all planar top surface regions of theinsulating material portions are within a same horizontal plane; atwo-dimensional array of metal plate clusters, wherein each of the metalplate clusters comprises a plurality of metal plates 34, each metalplate 34 including a horizontal metal plate portion 34H overlying aplanar top surface region of a respective insulating material portion 48and a connection metal portion 34C extending between the horizontalmetal plate portion 34H and a respective one of the metal interconnectstructures (46, 44, 425); and a two-dimensional array of light emittingdevice clusters bonded to the backplane 40 through respective bondingstructures (36, 48, 18), wherein each light emitting device clustercomprises a plurality of light emitting devices (10B, 10G, 10R)overlying a respective metal plate cluster.

In one embodiment, the light emitting device comprises compoundsemiconductor material portions 11 having irregular surface heightvariations and located on distal surfaces of the light emitting devices(10B, 10G, 10R), the distal surfaces being surfaces of the lightemitting devices facing away from the backplane 40. In one embodiment,the bonding structures (36, 48, 18) comprise a two-dimensional array ofbackplane-side bonding pads 36 located on top of the two-dimensionalarray of metal plate clusters, wherein each of the backplane-sidebonding pads 36 is located on a respective one of the horizontal metalplate portions 34H. In one embodiment, each of the light emittingdevices (10B, 10G, 10R) within the two-dimensional array of lightemitting device clusters includes a device-side bonding pad 17 that isbonded to a respective one of the backplane-side bonding pads 36 througha solder material portion 58.

In one embodiment, the metal interconnect structures (46, 44, 425) arearranged to provide a rectangular two-dimensional array of gap regionsGR in which the metal interconnect structures (46, 44, 425) are notpresent; the insulating material portions 48 are located over each ofthe gap regions GR; and the plurality of metal plates 34 overlies arespective one of the gap regions GR. In one embodiment, thetwo-dimensional array of light emitting device clusters has a sametwo-dimensional periodicity as the two-dimensional array of metal plateclusters, i.e., a first periodicity of M times Px1 along the firsthorizontal direction hd1 and a second periodicity of N times Py1 alongthe second horizontal direction hd2 in which M is an integer greaterthan 1 and N is an integer greater than 1.

In one embodiment, each of the connection metal portions 34C contacts atapered sidewall or a vertical sidewall of a respective one of theinsulating material portions 48 and a top surface of a respective metalinterconnect structure (46, 44, 425). In a first embodiment, theinsulating material portions 48 are arranged as a two-dimensional arrayof insulating mesa structures not directly contacting one another andhaving a same two-dimensional periodicity as the two-dimensional arrayof metal plate clusters. In a second embodiment, the insulating materialportions 48 are portions of a continuous insulating material layer 48Lthat covers a top surface of the backplane 40; and each connection metalportion 34C extends through a respective opening through the continuousinsulating material layer 48L.

The embodiments of the present disclosure provide the followingnon-limiting advantages. The planar top surface regions facilitateuniform bonding of LEDs by providing coplanar surfaces for LED bondingto the backplane. The insulating material portions may be pliable (i.e.,have a lower elastic module than the backplane substrate) to improvealignment of multiple light emitting devices during bonding.

According to an aspect of the present disclosure, a method of repairinga light emitting device assembly is provided. Specifically, the lightemitting device assembly formed by the processing steps of FIGS. 9-14Ccan have failed transfer sites at which a light emitting diode (10B,10G, 10R) failed to transfer for various reasons, which may includefailure to form bonded solder material portions 58 and/or failure todetach a light emitting diode from a source substrate and/or any otherreason.

Generally, a light emitting device comprising an imperfect array oflight emitting diodes (10B, 10G, 10R) bonded to a backplane 401 isprovided. The imperfect array is characterized by a structural deviationfrom a periodic two-dimensional array of light emitting diodes (10B,10G, 10R) by absence of at least one light emitting diode (10B, 10G,10R) at a respective vacancy location. As used herein, a “vacancylocation” refers to a site at which a light emitting diode would bepresent in a light emitting device in which all light emitting diodesare transferred as intended. but is not occupied by the actual lightemitting diode. In one embodiment, the light emitting device cancomprise multiple arrays of light emitting diodes (10B, 10G, 10R). Inone embodiment, each of the multiple arrays comprises light emittingdiodes (10B, 10G, 10R) that emit light at a respective peak wavelengththat differs among the multiple arrays. For example, the multiple arraysof light emitting diodes (10B, 10G, 10R) can include a first array ofblue-light-emitting diodes 10B, a second array of green-light-emittingdiodes 10G, and a third array of red-light-emitting diodes 10R. Amulti-color pixel includes at least one of each light emitting diode(10B, 10G, 10R). At least one of the multiple arrays can comprise animperfect array of light emitting diodes. Each array can have the sametwo-dimensional periodicity except at locations at which a lightemitting diode (10B, 10G, 10R) is missing, i.e., at vacancy locations.In one embodiment, the imperfect array of light emitting diodes (10B,10G, 10R) can comprise a plurality of vacancy locations at which aplurality of light emitting diodes are not present with a vacancypattern. In one embodiment, each of the multiple array of light emittingdiodes (10B, 10G, 10R) can comprise a respective vacancy pattern. Themulti-color pixels are also arranged in an array of multi-color pixelswhich overlaps the multiple arrays of light emitting diodes (10B, 10G,10R).

Referring to FIG. 15, a first repair source substrate 8S within an arrayof first light emitting diodes 10B is illustrated. The first repairsource substrate 8S and the array of first light emitting diodes 10B canbe the same as the first source substrate 8A with the first lightemitting diodes 10B illustrated in FIG. 9. As such, the array of firstlight emitting diodes 10B on the first repair source substrate 8S canhave the same periodicity as the array of first light emitting diodes10B on the first source substrate 8A.

A first carrier substrate 108 with a temporary adhesive layer 110Lthereupon can be provided. The first carrier substrate 108 can be anysubstrate with a planar surface, and can include an insulating material,a conductive material, a semiconducting material, or a combinationthereof. Preferably, the first carrier substrate 108 is transparent(e.g., at least 80% transparent) to laser radiation, such as infrared,visible or ultraviolet radiation, and can comprise a material such asglass or sapphire. A temporary adhesive layer 110L is applied over theplanar surface of the first carrier substrate 108. The temporaryadhesive layer 110L can be formed by spin-coating, and can have athickness in a range from 20 microns to 160 microns, although lesser andgreater thicknesses can also be employed. Alignment marks can be formedon the first carrier substrate 108 and/or in the temporary adhesivelayer 110L that correspond to the locations of the light emitting diodesto be transferred to the first carrier substrate 108.

The temporary adhesive layer 110L includes an adhesive material that canbe cured upon heating to a temperature within a first bondingtemperature range (which is also referred to as a first curingtemperature range), and debonds upon heating to a temperature within afirst debonding temperature range. The temporary adhesive layer 110L isthermally stable throughout the first bonding temperature range, andthermally decomposes only at a decomposition temperature that is abovethe first debonding temperature range. In one embodiment, the temporaryadhesive layer 110L is thermally stable at least up to 200 degreesCelsius, and decomposes at, or above, a decomposition temperature thatis above 200 degrees Celsius.

In an illustrative example, the temporary adhesive layer 110L caninclude a commercially available adhesive material, such as BrewerBOND®220. BrewerBOND® 220 material enables backside temperature processing upto 250° C. with minimal device wafer bowing. The bonding temperaturerange of BrewerBOND® 220 is from 130° C. to 170° C., and the debondingtemperature range of BrewerBOND® 220 is from 150° C. to 240° C. Withinthe temperature range from 150° C. to 170° C., BrewerBOND® 220 initiallyundergoes a bonding process and a debonding process gradually sets in asthe anneal process is prolonged. BrewerBOND® 220 is thermally stable upto 250° C. Upon debonding in a subsequent processing step, the firstcarrier substrate 108 can slide out with a small force.

Referring to FIGS. 16A-16C, a selected subset of the first lightemitting diodes 10B is attached to a respective cured portion of thetemporary adhesive layer 110L. The pattern of the selected subset of thefirst light emitting diodes 10B on the first repair source substrate 8S(as seen from the direction of the first light emitting diodes 10Btoward the first repair source substrate 8S) can be the mirror image ofthe pattern of the vacancy locations on the light emitting device underrepair (as seen from the direction of the light emitting diodes toward abackplane 401), i.e., the light emitting device including at least onemissing first light emitting diode 10B. An assembly of the first repairsource substrate 8S, the array of first light emitting diodes 10Bthereupon, at least one thermally cured portion of the temporaryadhesive layer 110L, and the first carrier substrate 108 is formed.

Generally, a light emitting device in which all subpixels emit light(i.e., are not defective in the sense that they emit light when they areturned on) and in which the light emitted by the subpixels is providedin a target range (e.g., desired peak wavelength range, luminescenceintensity range, etc.) is an adequately functioning light emittingdevice which does not require any repair. Repair of a light emittingdevice is needed only where the light emitting device includes at leastone subpixel that does not emit light when it is turned on (e.g.,because an LED is missing or non-functioning in a given subpixel) oremits light outside the target range. Each light emitting device can betested using an optical testing device to determine if each subpixelwithin the light emitting device emits light within a respective targetrange. If any one subpixel is defective, for example, either by notemitting light when it is turned on (e.g., because the LED in thesubpixel is missing or not properly bonded) or by emitting light outsidethe respective targetrange, then the defective pixel or pixels in thetested light emitting device is flagged for repair, and a set of mapsfor defective subpixels is generated, such as by using image processingsoftware. Each set of maps can include a first defect map that marks thecoordinates of defective first-type subpixels (due to defective first(e.g., blue) light emitting diodes 10B), a second defect map that marksthe coordinates of defective second-type subpixels (due to defectivesecond (e.g., green) light emitting diodes 10G), a third defect map thatmarks the coordinates of defective third-type subpixels (due todefective third (e.g., red) light emitting diodes 10R). Vacant (e.g.,vacancy) LED mounting sites in the tested light emitting device may beprovided by design in the form of extra spaces in some or all subpixelsfor bonding a repair light emitting diode, may be provided when a LED isunintentionally or intentionally omitted at a bonding site in a subpixeland/or may be formed by removal of a defective light emitting diodesbased on the set of maps generated from the testing. The pattern of theselected subset of the first light emitting diodes 10B on the firstrepair source substrate 8S can be the mirror image of the pattern ofdefective first subpixels (i.e., defective first light emitting diodes10B). While the present disclosure is described employing a repair LEDtransfer process for the first light emitting diodes 10B, the sameprocessing sequence can be employed for repair LED transfer processesfor the second light emitting diodes 10G and/or the third light emittingdiodes 10R (and any additional type of light emitting diodes present ina light emitting device) in order to restore the functionality of anydefective subpixel to an adequately functioning level.

Referring to FIG. 16A, a first configuration of the assembly is shown,in which the at least one thermally cured portion of the temporaryadhesive layer 110L comprises the entire thermally-cured temporaryadhesive layer 111L. The thermally cured temporary adhesive layer 111Lis derived from the temporary adhesive layer 110L of FIG. 15 by pressingthe first carrier substrate 108 toward the array of first light emittingdiodes 10B such that the array of first light emitting diodes 10B ispushed within a bottom portion of the temporary adhesive layer 110L, andsubsequently annealing the temporary adhesive layer 110L at a bondingtemperature, i.e., a temperature within the bonding temperature range,of the temporary adhesive layer 110L. The alignment marks can be used toposition the first light emitting diodes at the desired location. In oneembodiment, top portions of the first light emitting diodes 10B can beembedded within bottom portions of the temporary adhesive layer 110L.The protrusion depth of the top portions of the first light emittingdiodes 10B into the temporary adhesive layer 110L, and thus, into thethermally-cured temporary adhesive layer 111L, can be within a rangefrom 10% to 100% of the thickness of the thermally-cured temporaryadhesive layer 111L (which can be, for example, in a range from 20microns to 160 microns). The entirety of the temporary adhesive layer110L can be cured at a curing temperature, i.e., the bondingtemperature, in a furnace. Thus, each cured portion of the temporaryadhesive layer 110L comprises a portion of the thermally-cured temporaryadhesive layer 111L. The entire set of cured portions of the temporaryadhesive layer 110L constitutes the thermally-cured temporary adhesivelayer 111L.

Referring to FIG. 16B, a second configuration of the assembly is shown,in which the at least one thermally cured portion of the temporaryadhesive layer 110L comprises selectively laser-bonded temporaryadhesive portions 111 embedded in the temporary adhesive layer 110L. Thefirst carrier substrate 108 is pressed toward the array of first lightemitting diodes 10B such that the array of first light emitting diodes10B is pushed within a bottom portion of the temporary adhesive layer110L. In one embodiment, top portions of the first light emitting diodes10B can be embedded within bottom portions of the temporary adhesivelayer 110L. The protrusion depth of the top portions of the first lightemitting diodes 10B into the temporary adhesive layer 110L, and thus,into the thermally-cured temporary adhesive layer 111L, can be within arange from 10% to 100% of the thickness of the thermally-cured temporaryadhesive layer 111L (which can be, for example, in a range from 20microns to 160 microns). A laser beam 171 is employed to irradiate thedevice-side solder material portions 18 and/or the temporary adhesivelayer 110L on top of the selected subset of the first light emittingdiodes 10B through the transparent first carrier substrate 108 usingalignment marks for position of the irradiation. In one embodiment, thelaser beam 171 can be provided by a heating laser generating a laserbeam having an infrared wavelength. For example, the heating laser canbe a visible or infra-red laser having a wavelength in a range from 0.4micron to 20 microns, such as 1 to 2 microns. The power of the laserbeam 171 and the duration of laser irradiation at each selected firstlight emitting diode 10B can be selected such that the irradiatedportions of the temporary adhesive layer 110L are cured at a curingtemperature, i.e., at a bonding temperature, if the temporary adhesivelayer 110L is a thermoset adhesive layer or to melt the solder materialportion 18 to bond it to the temporary adhesive layer 110L. Thus, eachirradiated portion of the temporary adhesive layer 110L becomes alaser-bonded temporary adhesive portion 111. Generally, at least oneportion of the temporary adhesive layer 110L can be selectivelylaser-heated, and each cured portion of the temporary adhesive layer110L comprises a respective laser-heated portion of the temporaryadhesive layer 110L. The pattern of the selectively laser-bondedtemporary adhesive portions 111 can be the mirror image of the vacancylocations within the array of first light emitting diodes in the lightemitting device under repair. The laser-bonded temporary adhesiveportions 111 are embedded within uncured portions of the temporaryadhesive layer 110L.

Referring to FIG. 16C, a third configuration of the assembly is shown,in which the at least one thermally cured portion of the temporaryadhesive layer 110L comprises discrete thermally-cured temporaryadhesive portions 111′. In this case, at least one temporary adhesiveportion can be formed by patterning temporary adhesive layer 110L usingthe alignment marks to select the portions to pattern. For example, aphotoresist layer (not shown) can be applied over the top surface of thetemporary adhesive layer 110L while the first carrier substrate 108positioned below the temporary adhesive layer 110L. The photoresistlayer can be lithographically patterned with the same pattern as thepattern of the vacancy locations within the array of first lightemitting diodes in the light emitting device under repair. Portions ofthe temporary adhesive layer 110L that are not covered by the patternedphotoresist layer can be removed by an etch process, which may comprisean anisotropic etch process (such as a reactive ion etch process) or anisotropic etch process (such as a wet etch process). The photoresistlayer can be subsequently removed, for example, by dissolving in asolvent. The remaining portions of the temporary adhesive layer 110Lconstitutes the at least one temporary adhesive portion, which maycomprise a plurality of temporary adhesive portions. The first carriersubstrate 108 is pressed toward the array of first light emitting diodes10B such that the array of first light emitting diodes 10B is pushedwithin a bottom portion of a respective temporary adhesive portion. Inone embodiment, top portions of the first light emitting diodes 10B canbe embedded within bottom portions of the temporary adhesive layer 110L.The protrusion depth of the top portions of the first light emittingdiodes 10B into the at least one temporary adhesive portion, and thus,into the discrete thermally-cured temporary adhesive portions 111′, canbe within a range from 10% to 100% of the thickness of each temporaryadhesive portion (which can be, for example, in a range from 20 micronsto 160 microns). Generally, at least one temporary adhesive portion canbe thermally cured in a furnace. Each cured portion of the temporaryadhesive layer 110L can be formed by thermally curing a respectivetemporary adhesive portion. Less than the entirety of the temporaryadhesive layer 110L can be cured at the curing temperature, i.e., thebonding temperature. Each cured portion of the temporary adhesive layer110L comprises a respective discrete thermally-cured temporary adhesiveportion 111′.

FIGS. 17A-17C illustrate a respective subsequent processing step for theconfigurations of FIGS. 16A-16C, respectively, in which a laserirradiation process is employed to detach each first light emittingdiode 10B that needs to be transferred from the first repair sourcesubstrate 8S to the first carrier substrate 108. As discussed above, thepattern of the first light emitting diode 10B that needs to betransferred from the first repair source substrate 8S to the firstcarrier substrate 108 is the same as the mirror image of the pattern ofthe vacancy locations of the first light emitting diodes 10B in thelight emitting device under repair.

Referring to FIG. 17A, first replacement light emitting diodes 10B areselectively detached from the first repair source substrate 8S byselectively irradiating a bottom end of each of the first replacementlight emitting diodes 10B with a laser beam 173. In one embodiment, thelaser beam 173 can pass through the first repair source substrate 8Sbefore impinging on the bottom end of each first replacement lightemitting diode 10B. The wavelength of the laser beam 173 can be providedby an ablation laser, and can be different (e.g., shorter) from thewavelength of the heating laser. The wavelength of the ablation lasercan be, for example between 0.1 and 0.75 micron, such as 0.25 to 0.5micron. In one embodiment, the wavelength of the ablation laser can bewithin an ultraviolet range, i.e., within a range from 10 nm to 400 nm.The laser beam 173 can sequentially dissociate each first replacementlight emitting diode 10B from the first replacement source substrate 8S.In one embodiment, only those first replacement light emitting diodes10B are ablated that will fill the vacancy locations as will bedescribed in more in detail below.

Referring to FIG. 17B, first replacement light emitting diodes 10B areselectively detached from the first repair source substrate 8S byselectively irradiating with a laser beam 173 a bottom end of each ofthe first replacement light emitting diodes 10B that is bonded to thefirst carrier substrate 108. In this case, each first replacement lightemitting diode 10B adjoining a respectively selectively laser-bondedtemporary adhesive portion 111 can be detached from the firstreplacement source substrate 8S.

Referring to FIG. 17C, first replacement light emitting diodes 10B areselectively detached from the first repair source substrate 8S byselectively irradiating with a laser beam 173 a bottom end of each ofthe first replacement light emitting diodes 10B that is bonded to thefirst carrier substrate 108. In this case, each first replacement lightemitting diode 10B adjoining respective discrete thermally-curedtemporary adhesive portion 111′ can be detached from the firstreplacement source substrate 8S.

Referring to FIGS. 18A-18C, the assembly of the first carrier substrate108, cured temporary adhesive portions (111L, 111, 111′), and at leastone first replacement light emitting diode 10B can be detached from thefirst repair source substrate 8S by lifting off the assembly away fromthe first repair source substrate 8S. The at least one first replacementlight emitting diode 10B comprises a subset of the array of first lightemitting diodes 10B as originally provided on the first repair sourcesubstrate 8S. Each of the at least one first light emitting diode 10B isattached to the first carrier substrate 108 through a respective curedportion of the temporary adhesive layer 110L. The cured portion(s) ofthe temporary adhesive layer 110L can be the thermally-cured temporaryadhesive layer 111L (as illustrated in the first configuration of FIG.18A), the selectively laser-bonded temporary adhesive portions 111embedded in the temporary adhesive layer 110L (as illustrated in thesecond configuration of FIG. 18B), or as the discrete thermally-curedtemporary adhesive portions 111′ (as illustrated in the thirdconfiguration of FIG. 18C). The assembly of the first carrier substrate108, cured temporary adhesive portions (111L, 111, 111′), and at leastone first replacement light emitting diode 10B can have the same patternas the vacancy pattern for the first light emitting diodes 10B in thelight emitting device under repair (as seen from the direction of thefirst light emitting diodes 10B toward the first carrier substrate 108).

FIGS. 19 and 20 illustrate only the adhesive portion 111L for brevity.However, it should be understood that the steps in FIGS. 19 and 20 alsoapply to the adhesive portions 111 and 111′. Referring to FIG. 19, alayer stack including a second carrier substrate 208, a backside releaselayer 210L, and a temporary bonding layer 220L is provided. The layerstack can be formed, for example, by providing a second carriersubstrate 208, forming the backside release layer 210L on the secondcarrier substrate 208, and forming the temporary bonding layer 220Labove, and on, the backside release layer 210L. The second carriersubstrate 208 can be any substrate with a planar surface, and caninclude an insulating material, a conductive material, a semiconductingmaterial, or a combination thereof. Preferably, the second carriersubstrate 208 is transparent (e.g., at least 80% transparent) to laserradiation, such as infrared, visible or ultraviolet radiation, and cancomprise a material such as glass or sapphire

The backside release layer 210L can be formed over a planar surface ofthe second carrier substrate 208 by spin-coating. In one embodiment, thebackside release layer 210L comprises an adhesive material that can bereleased by laser irradiation, such as an excimer laser. For example,the backside release layer 210L comprises a material that is thermallystable, and adheres to the temporary bonding layer, at least up to 350degrees Celsius. In one embodiment, the backside release layer 210Lcomprises a material that absorbs at least 80% of light within awavelength in a range from 240 nm to 360 nm. The backside release layer210L is thermally stable up to a decomposition temperature, which can behigher than the decomposition temperature of the material of the curedportions of the temporary adhesive layer 110L. The backside releaselayer 210L can have a thickness in a range from 100 microns to 300microns, although lesser and greater thicknesses can also be employed.In an illustrative example, the backside release layer 210L can includea commercially available adhesive material, such as BrewerBOND® 701,which is an excimer laser release material that generates a minimallevel of stress. BrewerBOND® 701 is thermally stable up to 350° C.BrewerBOND® 701 can be debonded by laser irradiation with a laser beamhaving a wavelength in a range from 240 nm to 360 nm

In one embodiment, the backside release layer 210L may be an organic orinorganic polymer layer that can be dissolved in a solvent. For example,the backside release layer 210L may be a non-photosensitive organicpolymer layer that can be dissolved in an organic solvent. In this case,the entirety of the backside release layer 210L may be dissolved in asolvent in a subsequent release process. In another embodiment, thebackside release layer 210L may be a photosensitive organic polymerlayer that has an enhanced solubility upon irradiation with a radiationbeam, such as a a laser beam, which may be in an ultraviolet range or inan infrared range. In this case, subsequent irradiation with theradiation (e.g., laser) beam can facilitate dissolution of the backsiderelease layer 210L in a subsequent dissociation process, which canselectively remove laser-irradiated portions of the backside releaselayer 210L at a higher dissolution rate than unirradiated portions ofthe backside release layer 210L.

The temporary bonding layer 220L includes an adhesive material, whichcan be effective upon application and curing at room temperature or atan elevated temperature. The temporary bonding layer 220L is thermallystable throughout the first debonding temperature range, and thermallydecomposes only at a decomposition temperature that is above the firstdebonding temperature range. In one embodiment, the temporary bondinglayer 220L can be cured at a second bonding temperature range to providefull adhesion strength, and can have a second debonding temperaturerange at which debonding occurs. The second debonding temperature rangecan be higher than the first bonding temperature range of the temporaryadhesive layer 110L, and can be lower than the decomposition temperatureof the temporary adhesive layer 110L. In one embodiment, the temporarybonding layer 220L is thermally stable at least up to 250 degreesCelsius, and decomposes at, or above, a decomposition temperature thatis above 250 degrees Celsius, which may be above 300 degrees Celsius. Inone embodiment, the temporary bonding layer 220L can be thermally stableat least up to 300 degrees Celsius, and can decompose at a lowertemperature than the backside release layer 210L. In one embodiment, thetemporary bonding layer 220L can be thermally stable at least up to thedebonding temperature of the temporary adhesive layer 110L, i.e., theupper limit of the first debonding temperature range of the temporaryadhesive layer 110L. In one embodiment, the temporary bonding layer 220Lcan have a thickness in a range from 20 microns to 160 microns.

In an illustrative example, the temporary bonding layer 220L can includea commercially available adhesive material, BrewerBOND® 301. BrewerBOND®301 material enables backside temperature processing up to 300° C. withminimal device wafer bowing. BrewerBOND® 305 may be debonded by applyinga sheer force at room temperature from an underlying material layer, ormay be debonded from a backside release layer such as a layer ofBrewerBOND® 701 by laser irradiation.

Referring to FIG. 20, the first carrier substrate 108 and the secondcarrier substrate 208 can be pressed toward each other with at least onefirst replacement light emitting diode 10B therebetween. Each bottomportion of the at least one first replacement light emitting diode 10Bis pushed within a respective upper portion of the temporary bondinglayer 220L. The temporary bonding layer 220L can be subsequentlyannealed at a bonding temperature within the second temperature range ofthe temporary bonding layer 220L. In one embodiment, bottom portions ofthe first replacement light emitting diodes 10B can be embedded withinupper portions of the temporary bonding layer 220L. The protrusion depthof the bottom portions of the first replacement light emitting diodes10B into the temporary bonding layer 220L can be within a range from 10%to 100% of the thickness of the temporary bonding layer 220L. Theentirety of the temporary bonding layer 220L can be cured at a curingtemperature, i.e., the bonding temperature. Each of the at least onefirst replacement light emitting diode 10B can be attached to thetemporary bonding layer 220L.

Referring to FIGS. 21A-21C, the first carrier substrate 108 can bedetached from each cured portion of the temporary adhesive layer 110L,which may be the thermally-cured temporary adhesive layer 111L (asillustrated in the first configuration of FIG. 21A), the selectivelylaser-bonded temporary adhesive portions 111 embedded in the temporaryadhesive layer 110L (as illustrated in the second configuration of FIG.21B), or as the discrete thermally-cured temporary adhesive portions111′ (as illustrated in the third configuration of FIG. 21C). In oneembodiment, detachment of the first carrier substrate 108 from eachcured portion of the temporary adhesive layer 110L can be performed byelevating the temperature of the first carrier substrate 108 and eachcured portion of the temporary adhesive layer 110L above the debondingtemperature of the temporary adhesive layer 110L, i.e., above themaximum temperature of the second debonding temperature range at whichthe cured portion(s) (111L, 111, 111′) of the temporary adhesive layer110L thermally decompose(s). In this case, the decomposition temperatureof the temporary bonding layer 220L and the decomposition temperature ofthe backside release layer 210L can be higher than the decompositiontemperature of the temporary bonding layer 220L. For example, theassembly of the cured portion(s) of the temporary adhesive layer (111L,111, 111′), the first replacement light emitting diodes 10B, and thelayer stack of the second carrier substrate 208, the backside releaselayer 210L, and the temporary bonding layer 220L can be detached fromthe first carrier substrate 108 by pushing the first carrier substrate108 sideways after subjecting the cured portion(s) of the temporaryadhesive layer (111L, 111, 111′) to a temperature above thedecomposition temperature (i.e., a minimum temperature at which thematerial of the cured portion(s) of the temporary adhesive layer (111L,111, 111′) decomposes). The pattern of the at least one firstreplacement light emitting diode 10B on the second carrier substrate 208can be a mirror image of the pattern of the vacancy locations of thefirst light emitting diodes 10B in the light emitting device underrepair.

Referring to FIG. 22, each cured portion of the temporary adhesive layer(111L, 111, 111′) can be removed from the at least one first replacementlight emitting diode 10B. In one embodiment, removal of each curedportion of the temporary adhesive layer (111L, 111, 111′) can beperformed by dissolution in a solvent that selectively dissolves thematerial of the cured portion of the temporary adhesive layer (111L,111, 111′) without dissolving the material of the temporary bondinglayer 220L. For example, an alpha-olefin-based solvent can be employedto dissolve the material of the cured portion of the temporary adhesivelayer (111L, 111, 111′) without dissolving the material of the temporarybonding layer 220L. An illustrative example of the alpha-olefin-basedsolvents is 1-dodecene (C₁₀H₂₁CH═CH₂).

Optionally, the assembly of the assembly of the cured portion(s) of thetemporary adhesive layer (111L, 111, 111′), the first replacement lightemitting diodes 10B, and the layer stack of the second carrier substrate208, the backside release layer 210L, and the temporary bonding layer220L may be singulated, for example, by dicing or laser scribing, Inthis case, a diced unit that is subsequently employed to transfer the atleast one first replacement light emitting diodes 10B to the lightemitting device under repair is herein referred to as a repair coupon,or a “coupon.”

Referring to FIG. 23, a light emitting device under repair can bedisposed over the assembly of at least one first repair light emittingdiode 10B, the temporary bonding layer 220L, the backside release layer210L, and the second carrier substrate 208 such that vacancy locations10V of the first light emitting diodes 10B in the light emitting devicedirectly overlie a respective first repair light emitting diode 10B. Thepattern of the at least one first repair light emitting diode 10B on thesecond carrier substrate 208 can be the mirror image of the pattern ofthe vacancy locations of the first light emitting diodes 10B in thelight emitting device under repair. In one embodiment, the lightemitting device under repair can be a direct view device 500 withmissing light emitting diodes at the vacancy locations. The assembly ofthe first replacement light emitting diodes 10B and the layer stack ofthe second carrier substrate 208, the backside release layer 210L, andthe temporary bonding layer 220L can be aligned to the vacancy locationson the direct view device 500 such that each of the first replacementlight emitting diodes 10B directly underlies a respective vacancylocation 10V.

Referring to FIG. 24, the first replacement light emitting diodes 10Bcan be placed into a respective vacancy location 10V such that eachsource-side solder material portion 18 contacts a respective device-sidesolder material portion 38. Each first replacement light emitting diode10B can be bonded to a respective vacancy location within the imperfectarray of the direct view device 500. Specifically, a selective laserirradiation process can be performed to bond each first replacementlight emitting diode 10B to a backplane-side bonding pad 36 thatoverlies a respective vacancy location. The selective laser irradiationprocess induces reflow of a solder material between a backplane-sidebonding pad 36 and a respective first light emitting diode 10B.

In one embodiment, a laser beam (177A or 177B) can irradiate at leastone solder material portion (18, 38) to reflow the at least one soldermaterial portion (18, 38) and to form a respective bonded soldermaterial portion 58. In one embodiment, the laser beam 177A can passthrough the second carrier substrate and through the first replacementlight emitting diodes 10B to irradiate the at least one solder materialportion (18, 38) and to reflow the at least one solder material portion(18, 38). In another embodiment, if the backplane substrate 42 isoptically transparent, then the laser beam 177B can pass through thebackplane to heat the at least one solder material portion (18, 38). Thelaser beam 177B of the heating laser can pass through the gap region GRof the substrate 42 to avoid collateral heating of metal interconnectstructures (46, 44, 425) other than the irradiated metal plate 34, theirradiated backplane-side bonding pad 36, and the irradiated soldermaterial portions (18, 38). In one embodiment, the heating laser mayemploy infrared wavelength. For example, the heating laser can be avisible or infra-red laser having a wavelength in a range from 0.4micron to 20 microns, such as 1 to 2 microns, to avoid heating of thebackplane 40, while heating the at least one solder material portion(18, 38). In another embodiment, both laser beams (177A, 177B) can beused to irradiate the at least one solder material portion (18, 38)either simultaneously or sequentially.

Referring to FIG. 25, the backside release layer 210L can be irradiatedthrough the second carrier substrate 208 by a laser beam 187, which isherein referred to as a release laser beam. The wavelength of therelease laser beam can be, for example between 0.1 and 0.75 micron, suchas 0.25 to 0.5 micron. In one embodiment, the wavelength of the releaselaser beam can be within an ultraviolet range, i.e., within a range from10 nm to 400 nm. In one embodiment, the wavelength of the release laserbeam can be in a range from 240 nm to 360 nm. The release laser beam cancontinuously scan the entire area of the backside release layer 210L.The backside release layer 210L and the second carrier substrate 208 aredetached from the temporary bonding layer 220L upon irradiation by therelease laser beam.

In another embodiment, the backside release layer 210L may be removed bydissolution in a solvent. The solvent may be an organic solvent such asacetone, isopropyl alcohol, methyl alcohol, ethyl alcohol, benzene,toluene, or chlorinated or fluorinated derivatives thereof, or anorganic or inorganic etching compound. For example, the solvent maycause the backside release layer 210L to swell and become mechanicallysheared off. In another embodiment, the backside release layer 210Lcomprises a photosensitive polymer, and removing the at least one firstlight emitting diode 10B to form at least one vacancy location withinthe light emitting device can be performed by a laser beam that passesthrough, and increases a dissolution rate in a solvent for a portion ofthe photosensitive polymer. In this case, irradiated portions of thephotosensitive polymer can be removed at a higher dissolution rate,thereby accelerating the removal process for the backside release layer210L.

In yet another embodiment, the backside release layer 210L may be athermal or mechanical release layer. For example, the backside releaselayer 210L may be a thermal release layer which is dissolved by heating.The heating may be performed by a laser (as described above), a heatlamp or a furnace. Alternatively, the backside release layer 210L may bea mechanical release layer, such as an organic adhesive layer, which canbe detached by applying a mechanical force (e.g., shear force and/orpulling force) thereto.

Referring to FIG. 26, the temporary bonding layer 220L can besubsequently removed from the first light emitting diodes 10B. Forexample, the temporary bonding layer 220L can be removed by dissolutionin a solvent, or can be removed by a thermal treatment above thedecomposition temperature. A suitable clean in a solvent may beperformed to clean residues of the temporary bonding layer 220L. Forexample, an oxidizing plasma or an oxidizing solvent stripping processsuch as ozone plasma stripping, Piranha® solution, or RCA cleaning maybe employed.

In one embodiment, the light emitting device can comprise an array oflight emitting diodes without any vacancy location within the array upontransfer of the first repair light emitting diodes 10B. Alternatively,the light emitting device can comprise at least one imperfect array oflight emitting diodes including vacancy locations 10V of light emittingdiodes that emit radiation at a different peak wavelength than the firstlight emitting diodes 10B. For example, the light emitting device cancomprise an imperfect array of second light emitting diodes 10Gincluding respective vacancy locations and/or an imperfect array ofthird light emitting diodes 10R including respective vacancy locations.In this case, the processing steps of FIGS. 15-26 can be repeated foreach imperfect array of light emitting diodes to provide respectivereplacement light emitting diodes to the vacancy locations, therebyrepairing each imperfect array into a “perfect array” in which vacancylocations 10V are absent. Thus, full functionality can be provided tothe light emitting device under repair.

In one embodiment, the light emitting device comprising an array ofmulti-color pixels that includes multiple arrays of light emittingdiodes, and each of the multiple arrays comprises light emitting diodesthat emit light at a respective peak wavelength that differs among themultiple arrays. The multiple arrays can comprise an imperfect array oflight emitting diodes.

In one embodiment, the light emitting diodes in the imperfect array andthe first light emitting diodes emit light at a first peak emissionwavelength, and the light emitting device comprising the imperfect arrayof light emitting diodes further comprises an additional imperfect arrayof light emitting diodes comprising additional light emitting diodesthat emit light at a second peak emission wavelength that is differentfrom the first peak emission wavelength. In this case, at least onesecond light emitting diode emitting light at the second peak emissionwavelength can be transferred to vacancy locations within the additionalimperfect array by sequentially transferring the at least one secondlight emitting diode to two additional carrier substrates and then tothe backplane.

Although the foregoing refers to particular preferred embodiments, itwill be understood that the invention is not so limited. It will occurto those of ordinary skill in the art that various modifications may bemade to the disclosed embodiments and that such modifications areintended to be within the scope of the invention. Where an embodimentemploying a particular structure and/or configuration is illustrated inthe present disclosure, it is understood that the present invention maybe practiced with any other compatible structures and/or configurationsthat are functionally equivalent provided that such substitutions arenot explicitly forbidden or otherwise known to be impossible to one ofordinary skill in the art.

What is claimed is:
 1. A method of repairing a light emitting deviceassembly, comprising: providing a repair source substrate with an arrayof first light emitting diodes; providing a first carrier substrate witha temporary adhesive layer thereupon; forming a first assembly includingthe first carrier substrate and at least one first light emitting diodethat is a subset of the array of first light emitting diodes, whereinthe at least one first light emitting diode is attached to the firstcarrier substrate through a respective portion of the temporary adhesivelayer and detached from the repair source substrate; providing a secondcarrier substrate with a temporary bonding layer thereupon; attachingthe at least one first light emitting diode to the temporary bondinglayer; detaching the first carrier substrate from each portion of thetemporary adhesive layer; removing each portion of the temporaryadhesive layer from the at least one first light emitting diode;providing a light emitting device comprising at least one vacancylocation and an array of light emitting diodes bonded to a backplane;and bonding the at least one first light emitting diode to therespective at least one vacancy location within the light emittingdevice.
 2. The method of claim 1, wherein: the light emitting devicecomprises a plurality of vacancy locations at which a plurality of lightemitting diodes are not present with a vacancy pattern; and the firstassembly includes a plurality of first light emitting diodes with a samepattern as the vacancy pattern.
 3. The method of claim 1, furthercomprising: forming a backside release layer on the second carriersubstrate, wherein the temporary bonding layer is formed above thebackside release layer; removing the backside release layer afterattaching the at least one first light emitting diode to the respectivevacancy location; and removing the temporary bonding layer after bondingthe at least one first light emitting diode to the respective at leastone vacancy location.
 4. The method of claim 3, where the backsiderelease layer is removed by dissolution in a solvent.
 5. The method ofclaim 4, wherein: the backside release layer comprises a photosensitivepolymer; and the backside release layer is removed by passing a laserbeam through the photosensitive polymer to increases a dissolution ratein a solvent for a portion of the photosensitive polymer.
 6. The methodof claim 3, wherein the backside release layer comprises a material thatis thermally stable, adheres to the temporary bonding layer at atemperature of at least up to 350 degrees Celsius, and absorbs at least80% of radiation within a wavelength in a range from 240 nm to 360 nm.7. The method of claim 3, wherein the temporary bonding layer isthermally stable at least up to 300 degrees Celsius, and decomposes at alower temperature than the backside release layer.
 8. The method ofclaim 1, wherein the temporary adhesive layer is thermally stable atleast up to 200 degrees Celsius, and decomposes at a lower temperaturethan the temporary bonding layer.
 9. The method of claim 1, wherein: thetemporary adhesive layer has a thickness in a range from 20 microns to160 microns; and the temporary bonding layer has a thickness in a rangefrom 20 microns to 160 microns.
 10. The method of claim 1, furthercomprising curing an entirety of the temporary adhesive layer at acuring temperature.
 11. The method of claim 1, further comprisingselectively laser-heating at least one portion of the temporary adhesivelayer, wherein each portion of the temporary adhesive layer comprises arespective laser-heated portion of the temporary adhesive layer to whichthe at least one light emitting diode is attached.
 12. The method ofclaim 1, further comprising: forming at least one temporary adhesiveportion by patterning temporary adhesive layer; and thermally curing theat least one temporary adhesive portion, wherein each portion of thetemporary adhesive layer is formed by thermally curing a respectivetemporary adhesive portion.
 13. The method of claim 1, furthercomprising selectively detaching each of the at least one first lightemitting diode within the first assembly from the repair sourcesubstrate by selectively irradiating a bottom end of each of the atleast one first light emitting diode with a laser beam.
 14. The methodof claim 11, wherein the laser beam passes through the repair sourcesubstrate before impinging on the bottom end of each of the at least onefirst light emitting diode.
 15. The method of claim 1, whereindetachment of the first carrier substrate from each portion of thetemporary adhesive layer is performed by elevating a temperature of thefirst carrier substrate and each portion of the temporary adhesive layerabove a debonding temperature of the temporary adhesive layer.
 16. Themethod of claim 1, wherein the temporary bonding layer is thermallystable at least up to the debonding temperature of the temporaryadhesive layer.
 17. The method of claim 1, wherein removal of eachportion of the temporary adhesive layer is performed by dissolution inan alpha-olefin-based solvent.
 18. The method of claim 1, whereinbonding the at least one first light emitting diode to the respective atleast one vacancy location is performed by a selective laser irradiationprocess that induces reflow of a solder material between abackplane-side bonding pad and a respective first light emitting diode.19. The method of claim 18, wherein a laser beam passes through thesecond carrier substrate and the temporary bonding layer during theselective laser irradiation process.
 20. The method of claim 18, whereina laser beam passes through the backplane during the selective laserirradiation process.
 21. The method of claim 1, wherein: the lightemitting device comprising an array of multi-color pixels that includesmultiple arrays of light emitting diodes; and at least one of themultiple arrays comprises at least one vacancy location and lightemitting diodes.
 22. The method of claim 21, wherein: the first lightemitting diodes emit light at a first peak emission wavelength; and themethod further comprises transferring at least one second light emittingdiode emitting light at the second peak emission wavelength differentfrom the first peak emission wavelength to the at least one vacancylocations by sequentially transferring the at least one second lightemitting diode to two additional carrier substrates and then to thebackplane.